The unusual transport of vitamin B12 across the placenta is being investigated. The early studies have involved identification, characterization, and solubilization of a transcobalamin II-B12 receptor in human placental membrane fractions. Current work involves studies of the subcellular route taken by this vitamin in its transport through the placenta. Studies looking at uptake and metabolism of B12 by placental mitochondria are being performed. The surface receptor for TCII-B12 is being purified. BIBLIOGRAPHIC REFERENCE: Friedman, P.A., Shia, M.A., and Wallace, J.K. A Saturable High Affinity Binding Site for Transcobalamin II-Vitamin B12 Complexes in Human Placental Membrane Preparations. J. Clin. Invest. 59 (1977), 51-58.